﻿19 1 6] MIC HELL — RICH A RDIA AFRICA X A 329 



fig. 11a. As fertilization has been demonstrated at this stage, 

 it is safe to conclude that the embryo sac is mature. It is possible 

 that Gow's figure was taken from a younger ovule. 



Fertilization 



The process of fertilization is rather difficult to demonstrate 

 in Richardia. Quite possibly it does not occur in the majority of 

 ovules, as even in its native habitat Richardia does not set seed 

 freely. It appears that this failure to set seed is seldom due to a 

 lack of organization of the embryo sac, or to sterility of the pollen 

 grains, but probably may be accounted for by the absence from the 

 plants of an efficient pollinating agent. In this connection it is 

 significant to note that it is rare to find one pollinated ovary alone 

 on an inflorescence. If pollination has occurred, usually most of 

 the ovaries have been pollinated. 



Church (5) has reported that small flies and green aphids 

 visit the inflorescence when in cultivation in England, but adds 

 that they do not seem to be of much service in pollination. The 

 same thing, if earwigs be added to the list, occurs in the Cape 

 Peninsula, where the remains of these insects are to be found at 

 the base of inflorescences which obviously have not been pollinated. 



A large number of ovaries were collected from inflorescences 

 of widely differing ages. The embryo sac is mature by the time 

 the spathe opens, and persists in this stage for an indefinite length 

 of time. It has even been found in an ovary taken from an inflores- 

 cence whose spathe was withering. 



Even if fertilization does not occur, the ovaries enlarge. It has 

 not been possible, through lack of opportunity of proving it experi- 

 mentally, to demonstrate whether the egg is capable of being fer- 

 tilized the whole time the spathe is open, or whether the fertilization 

 period is restricted to a longer or shorter time dating from the 

 opening of the spathe. 



Only one case of undoubted fertilization has been observed. 

 This is shown in fig. 13, in which the pollen tube is seen passing 

 through a synergid and the male nucleus is fusing with the egg 

 nucleus. "Double fertilization" has not been observed. In the 

 lower part of the ovule in which fertilization is being effected, the 



